Methane hydrates

Methane hydrate isn’t a familiar term to most, but it is gaining popularity in the energy sector. In the realm of energy R&D, methane hydrates are being evaluated as a potential fuel for the future. Some believe there is enough methane in the form of hydrates—methane locked in ice—to supply energy for hundreds, maybe thousands, of years.

The fuel of the future may be ice that burns

Methane hydrates, a promising natural gas resource, are believed to reside throughout the globe in sea-floor sediments and permafrost.

Lorie Langley, who is leading ORNL’s Gas Hydrate program for the Fossil Energy Program, believes ORNL can contribute significantly to DOE’s and Congress’s research agenda. Last month President Clinton signed the Methane Hydrate Research and Development Act, which authorizes approximately $50 million over five years to develop an understanding of the nature, behavior and abundance of this clean-burning energy resource.

Explains Langley, “Gas hydrates are clathrate compounds. A clathrate is simply a structure in which water molecules under certain conditions bond to form an ice-like cage that encapsulates a gas molecule, known as a guest molecule. When that guest is a methane molecule, you have methane hydrate.”

Methane hydrates, which form at low temperature and high pressure, are found in sea-floor sediments and the arctic permafrost. They can be scattered through several-hundred-meter depths and at various concentrations. The gas hydrates being evaluated by ORNL researchers are methane hydrates and carbon dioxide hydrates.

Although some research has been carried out in the past, little is known about the location, formation, decomposition, or actual quantities of methane hydrates. However, national and international research and exploration over the last 20 years by various governmental and industrial entities have resulted in general agreement that methane hydrates should be evaluated as a potential primary energy source for the future.

The growing demand for natural gas points to a need for this resource, Langley says. “The United States consumes about 21 trillion cubic feet of natural gas per year. We import three percent of that. Demand is expected to grow to 32 trillion cubic feet by 2020.”

The natural gas infrastructure is growing also. Much of industry has already converted to natural gas. Public utilities are headed that way as well.

DOE’s research agenda is structured around four major R&D elements: resource characterization, production, global carbon cycle, and safety and sea-floor stability.

Estimates on how much energy is stored in methane hydrates range from 350 years' supply to 3500 years'.

Resource characterization: This is essentially the baseline research toward understanding how methane hydrates behave, where and how they occur and what energy potential they actually represent. This work will require extensive data management, computer modeling and laboratory and field studies.

Production: Methods of harvesting methane hydrates will have to be developed. Langley emphasized that production methods for methane hydrates will be evaluated and will probably be similar to those of the oil and gas industry: depressurization, thermal stimulation or possibly solvent injection.

Global carbon cycle: Since methane is a greenhouse gas, understanding methane as a primary gas or a trace gas will be important in today’s climate change initiatives. Hydrates are being evaluated as a potential storage mechanism for CO2 sequestration and for storing methane for use as a transporation fuel. Langley points out that although methane when burned is a clean fuel, more information is needed on the emissions from various methane sources to fully understand its atmospheric implications.

Safety and sea-floor stability: The oil and gas industry continues to explore deeper beneath the ocean floor. Industry has concerns about drilling through hydrate zones, which can destabilize supporting foundations for platforms and production wells. The disruption to the ocean floor also could result in surface slumping or faulting, which could endanger work crews and the environment.

Hydates, the small specks, have been formed in ESD's Sea-floor Process Simulator.

Langley and ORNL Fossil Energy Program Manager Rod Judkins recently wrapped up a call for proposals for methane hydrate research. Research is already in progress: ORNL researchers currently are developing and producing hydrates in the Sea-floor Process Simulator in the Environmental Sciences Division and have completed support for the installation of a research well in Canada’s Northwest Territories. Data fusion and resource assessment activities are under way in the Computer Science and Mathematics Division to develop a model that will better estimate the resource. Proposed projects in crystallography by the Metals and Ceramics Division will provide hydrate structural data through neutron diffraction.

“Estimates on how much energy is stored in methane hydrates range from 350 years’ supply to 3500 years’ supply based on current energy consumption. That reflects both the potential as a resource and how little we really know about the resource,” Langley says.

“ORNL is and will continue to contribute to all four of the research areas. Methane hydrates have the potential to offer a clean source of energy, but we need to know much more about this ice.”—B.C.